Re: Exporting which partitions to md-configure

Kyle Moffett
2006-01-31T06:42:56Z

On Jan 30, 2006, at 21:01, Neil Brown wrote:
> On Monday January 30, mrmacman_g4@mac.com wrote:
>> On Jan 30, 2006, at 20:10, Neil Brown wrote:
>>> On Monday January 30, hpa@zytor.com wrote:
>>>> Any feeling how best to do that? My current thinking is to
>>>> export a "flags" entry in addition to the current ones,
>>>> presumably based on "struct parsed_partitions->parts[].flags" fs/
>>>> partitions/ check.h), which seems to be what causes
>>>> md_autodetect_dev() to be called.
>>>
>>> I think I would prefer a 'type' attribute in each partition that
>>> records the 'type' from the partition table. This might be more
>>> generally useful than just for md. Then your userspace code
>>> would have to look for '253' and use just those partitions.
>>
>> Well, for an MSDOS partition table, you would look for '253', for
>> a Mac partition table you could look for something like
>> 'Linux_RAID' or similar (just arbitrarily define some name
>> beginning with the Linux_ prefix), etc. This means that the
>> partition table type would need to
>> be exposed as well (I don't know if it is already).
>
> Mac partition tables doesn't currently support autodetect (as far
> as I can tell). Let's keep it that way.

Well, no, the point would definitely *NOT* be to add kernel-level
autodetect of stuff in the Mac partition tables. The point would be
to export the partition-table-format and partition-type information
to userspace. That way a custom mdadm-control-script could have a
config file with "AUTODETECT_TYPE=Linux_RAID" or
"AUTODETECT_TYPE=253" or "AUTODETECT_TYPE=<insert EFI UUID here>",
etc. The whole detection thing could be configured and done in
userspace based on partition table info provided by the kernel if
desired, or mdadm could just scan all disks for RAID headers like it
does now. The idea would be that any autodetection would be
completely out of the kernel and userspace's responsibility; the
kernel would just export info to make it easier.

Cheers,
Kyle Moffett

--
Unix was not designed to stop people from doing stupid things,
because that would also stop them from doing clever things.
-- Doug Gwyn